From f17428a009c8fc544b6244bab951a153dff023eb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20B=C3=B8e?= <sebastian.boe@nordicsemi.no>
Date: Wed, 29 Jan 2020 15:39:33 +0100
Subject: [PATCH] cmake: Have gperf be opt-out instead of mandatory
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gperf is only used when CONFIG_USERSPACE is enabled. Users that use
arch's that don't support CONFIG_USERSPACE, or happen to not never
enable CONFIG_USERSPACE should not be artificially required to install
gperf.

This change makes gperf optional by moving it's presence-check to it's
usage.

Signed-off-by: Sebastian Bøe <sebastian.boe@nordicsemi.no>
---
 CMakeLists.txt         | 4 ++++
 cmake/host-tools.cmake | 4 +---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d4ac0716daf..c786770bee4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -812,6 +812,10 @@ if(CONFIG_ARM AND CONFIG_USERSPACE)
     )
   add_custom_target(priv_stacks DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/${PRIV_STACKS})
 
+  if(${GPERF} STREQUAL GPERF-NOTFOUND)
+    message(FATAL_ERROR "Unable to find gperf")
+  endif()
+
   # Use gperf to generate C code (PRIV_STACKS_OUTPUT_SRC_PRE) which implements a
   # perfect hashtable based on PRIV_STACKS
   add_custom_command(
diff --git a/cmake/host-tools.cmake b/cmake/host-tools.cmake
index 6858f2f3f82..3bd3e4fd9c3 100644
--- a/cmake/host-tools.cmake
+++ b/cmake/host-tools.cmake
@@ -75,13 +75,11 @@ if(${CMAKE_MATCH_1} VERSION_LESS ${MIN_DTC_VERSION})
 endif()
 endif(DTC)
 
+# gperf is an optional dependency
 find_program(
   GPERF
   gperf
   )
-if(${GPERF} STREQUAL GPERF-NOTFOUND)
-  message(FATAL_ERROR "Unable to find gperf")
-endif()
 
 # openocd is an optional dependency
 find_program(